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Wyświetlanie 1-15 z 22
Tytuł:
Atomic Nucleus as Chaotic Quantum Many-Body System
Autorzy:
Zelevinsky, V.
Powiązania:
https://bibliotekanauki.pl/articles/1190111.pdf
Data publikacji:
2015-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.45.Mt
24.60.Lz
24.80.+y
24.10.Pa
Opis:
Quantum many-body chaos is described as a practical (theoretical, experimental, and computational) instrument in physics of mesoscopic systems of interacting particles. Using mainly nuclear physics applications, it is shown that interactions of constituents create stationary states of high complexity with respect to the nean-field basis with observable properties smoothly changing along the spectrum. Both local Gaussian orthogonal ensemble type features and the global evolution along the spectrum are used to understand the many-body physics and define thermodynamic properties of isolated mesoscopic objects. Among the examples discussed, especially interesting is a chaotic enhancement of weak perturbations illustrated by a large parity violation in neutron resonances on heavy nuclei. Artificially introduced chaotic elements are used to explore the nuclear landscape and predict phase transformations.
Źródło:
Acta Physica Polonica A; 2015, 128, 6; 1008-1016
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
(n,2n) and (n,3n) Neutron Induced Reaction Cross Sections above 8 MeV
Autorzy:
Salman, H.
Ünal, R.
Oruncak, B.
Akçaalan, U.
Yalim, H.
Powiązania:
https://bibliotekanauki.pl/articles/1401991.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
24.10.-i
Opis:
Neutron induced reaction cross sections for (n,2n) and (n,3n) have been calculated in the energy range between 8 MeV and 26 MeV. Calculations were made for the target nuclei; $\text{}^{45}Sc,$ $\text{}^{59}Co,$ $\text{}^{89}Y,$ $\text{}^{93}Nb,$ $\text{}^{103}Rh,$ $\text{}^{169}Tm,$ $\text{}^{175}Lu,$ $\text{}^{181}Ta,$ $\text{}^{197}Au,$ $\text{}^{209}Bi$. Calculated results were compared with the available data in EXFOR. Model calculations of present data indicated clearly that some reported data from measurements failed to separate (n,2n) and (n,3n) contributions.
Źródło:
Acta Physica Polonica A; 2015, 128, 2B; B-231-B-235
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cooper Pair with Nonzero Momentum in System with Spin Dependent Mass of Quasiparticles
Autorzy:
Kaczmarczyk, J.
Spałek, J.
Powiązania:
https://bibliotekanauki.pl/articles/2047323.pdf
Data publikacji:
2007-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.24.+q
71.10.Li
Opis:
We consider a single Cooper pair with the spin dependent quasiparticle masses, with and without applied magnetic field. Such situation takes place for the strongly correlated electron systems, where a relatively strong Hubbard interaction differentiates the quasiparticle states in the majority- and the minority-spin subbands. In that situation, the two spin subbands in an applied magnetic field are not only shifted one with respect to the other, but also distorted differently, which results from the electronic correlations. Under these circumstances, the fermionic particles composing the Cooper pair, are quantum mechanically distinguishable. In result, the Cooper pair has a nonzero momentum (i.e. produces a stationary current in a similar manner as electron in the Bloch state), and there exists a critical value of the attractive interaction, below which the bound Cooper-pair state is not formed. The presence of the applied field (included via the Zeeman term) does not alter the picture qualitatively. Importance of these results for the formation of the Fulde-Ferrell-Larkin-Ovchinnikov phase in strongly correlated systems is mentioned.
Źródło:
Acta Physica Polonica A; 2007, 111, 4; 595-602
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cross Sections Calculation of (γ,N) Reactions for Some Elements
Autorzy:
Karpuz, N.
Boz, M.
Mavi, B.
Akkurt, I.
Powiązania:
https://bibliotekanauki.pl/articles/1402484.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
24.10.-i
25.20.-x
Opis:
Photonuclear processes can play an important role in the detection of nuclear materials. For this purpose, in this study, the (γ,n) and (γ,p) cross sections as functions of photon energy in medium weight nuclei were calculated. Calculations have been made of the cross sections for some of the (γ,n) and (γ,p) reactions in $\text{}^{28}Si,$ $\text{}^{32}S,$ $\text{}^{56}Fe$ and $\text{}^{63}Cu$ nuclei using the TALYS 1.6 nuclear code with incident photons of 7-40 MeV. These calculated cross sections are compared with each other and with the earlier experimental results from the literature (EXFOR). Calculated results ($\text{}^{56}Fe(γ,n),$ $\text{}^{63}Cu(γ,n),$ $\text{}^{56}Fe(γ,p)$ and $\text{}^{63}Cu(γ,p)$ cross sections) are in very good agreement with the experimental data. However, because of the Coulomb barrier, the photoproton cross sections for $\text{}^{32}S,$ $\text{}^{56}Fe$ and $\text{}^{63}Cu$ target nuclei, are smaller than the photoneutron cross sections.
Źródło:
Acta Physica Polonica A; 2015, 128, 2B; B-411-B-413
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Photoneutron Cross Sections and the Effect of Gamma Strength Functions for W, Ag, Nb
Autorzy:
Karpuz Demir, N.
Çetin, B.
Powiązania:
https://bibliotekanauki.pl/articles/1031930.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
24.10.-i
25.20.-x
Opis:
In nuclear reactions the usage of high energy gamma particles, as projectiles, has some essential advantages for studying of nuclear structure and reaction mechanisms. In this work, (γ,n) reaction cross sections of ¹⁸⁶W, ¹⁰⁷Ag and ⁹³Nb have been calculated with TALYS 1.6 nuclear reaction simulation code. The main aim of this study is to investigate the effects of preequilibrium and the gamma strength functions on ¹⁸⁶W, ¹⁰⁷Ag and ⁹³Nb. The calculated results have been discussed and compared with the experimental data.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 1076-1079
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excitation functions of (d,n) reactions on some light nuclei
Autorzy:
Noori, S.
Karpuz, N.
Akkurt, İ.
Powiązania:
https://bibliotekanauki.pl/articles/1068511.pdf
Data publikacji:
2016-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
25.45.De
24.10.Lx
Opis:
Nuclear reactions of the induced deuteron particles with light nuclei have been investigated in the history of nuclear physics. In this study, excitation functions for the deuteron reactions ⁶Li(d,n)⁷Be, ¹²C(d,n)¹³N, ¹⁶O(d,n)¹⁷F have been calculated by using Monte Carlo nuclear reaction simulation code TALYS 1.6, considering equilibrium and pre-equilibrium effects. The calculated theoretical (d,n) excitation functions are compared to the experimental reaction cross-sections in the literature.
Źródło:
Acta Physica Polonica A; 2016, 130, 1; 484-486
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Alpha Head on Collision with a Fixed Gold Nucleus, Taking into Account the Relativistic Rest Mass Variation as Implied by Mass-Energy Equivalence
Autorzy:
Yarman, T.
Arik, M.
Kholmetskii, A.
Altintas, A.
Ozaydin, F.
Powiązania:
https://bibliotekanauki.pl/articles/1195230.pdf
Data publikacji:
2014-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
21.60.-n
24.10.Jv
Opis:
We reformulate the Rutherford scattering of alpha particle for a head on collision, taking into account the rest mass variation of the particle, as implied by the energy conservation law. Our relativistic reformulation (which includes the energy conservation) constitutes a new example for the breakdown of the Lorentz invariance. Briefly speaking, even at rest or during the whole scattering process, the distance between the alpha particle and the gold nucleus is not invariant but depends on the frame of the observer attached to either object. According to our relativistic reformulation, we also provide a new set of Lorentz transformations.
Źródło:
Acta Physica Polonica A; 2014, 125, 2; 618-619
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculation of Gamma Strength Functions for Photonucleon Reactions
Autorzy:
Karpuz, N.
Mavi, B.
Akkurt, İ.
Powiązania:
https://bibliotekanauki.pl/articles/1402486.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
24.10.-i
25.20.-x
Opis:
The cross section for (γ,N) reaction is important for investigation of nuclear structure, especially in low-energy giant dipole resonance (GDR). The total cross sections of $\text{}^{12}C(γ,n)^{11}C$ and $\text{}^{12}C(γ,p)^{11}B$ reactions, calculated using TALYS 1.2 nuclear code, are 15.5 to 40 MeV and 15 to 110 MeV, respectively. In the calculations, the default pre-equilibrium models and Brink-Axel Lorentzian model in all of the gamma strength functions have been used. The effects of the gamma strength function on the cross section exchange data has determined the most compatible model type. The results are compared with the experimental data from the EXFOR database and the evaluated nuclear data from TENDL-2012. Our calculated results are in good agreement with the previously reported experimental results.
Źródło:
Acta Physica Polonica A; 2015, 128, 2B; B-414-B-416
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Susceptibility of Mesoscopic Systems
Autorzy:
Wałcerz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1955458.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.24.+q
71.70.Di
71.15.-m
Opis:
The Onsager description of de Haas-van Alphen oscillations and the magnetic translation group approach are combined in order to argue that the magnetic susceptibility of mesoscopic systems is assumed to reveal some features different than those of a bulk sample. Firstly, due to a discrete nature of magnetic field that has to be taken into account while dealing with the mesoscopic scale phenomena, the susceptibility should vary in a discrete way, too. Secondly, the susceptibility should depend on both the size and the shape of the system.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 285-287
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neutron resonances: widths distribution versus the Porter-Thomas law
Autorzy:
Sokolov, V.
Powiązania:
https://bibliotekanauki.pl/articles/1050933.pdf
Data publikacji:
2017-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.45.Gg
24.60.Lz
05.45.Mt
Opis:
The neutron resonance scattering off heavy nuclei is a paradigmatic example of the chaotic processes that are well described within the framework of the standard Random Matrix Theory (RMT). In zero approximation of non-overlapping resonances, the resonance width distribution is given by the standard Porter-Thomas law (PTD) dw/dx= e^{-x/2}/√(2πx), where x=Γ/⟨Γ⟩ is the resonance width measured in the units of its mean value. We analyze the influence of the resonance overlapping and show that the experimentally observed deviations from of the PTD arise due to the influence of a moderate number of neighboring resonances located inside a restricted energy interval within which the mean level spacing D remains constant.
Źródło:
Acta Physica Polonica A; 2017, 132, 6; 1704-1706
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chaotic Scattering: Exact Results and Microwave Experiments
Autorzy:
Guhr, T.
Powiązania:
https://bibliotekanauki.pl/articles/1190089.pdf
Data publikacji:
2015-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.45.Mt
03.65.Nk
24.60.Dr
Opis:
Scattering experiments are indispensable for the study of classical and quantum systems. In the Heidelberg approach, universal features are addressed by assuming that the reaction zone is fully quantum chaotic. Although it stems from nuclear physics, it later on turned out to be applicable to a large variety of systems on different scales, including classical wave systems. For a long time, the distribution of the off-diagonal scattering-matrix elements resisted analytical treatment. I review two recent studies in which my collaborators and I fully solved this problem. We also carried out a comparison with data from microwave experiments.
Źródło:
Acta Physica Polonica A; 2015, 128, 6; 963-967
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
INDRA: A 4π Detector for Nuclear Dynamics and Thermodynamics Studies
Autorzy:
Rivet, M.
Powiązania:
https://bibliotekanauki.pl/articles/1402640.pdf
Data publikacji:
2015-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
25.70.Mn
25.70.Pq
24.60.Ky
Opis:
This paper reports on some topics presently studied by the INDRA collaboration in nuclear dynamics and thermodynamics. We shall show information on the density dependence of the symmetry term of the nuclear equation of state. A possible origin of multifragmentation and fragment formation will be demonstrated. Finally we report on an experiment aiming at determining the influence of isospin on the nucleus level density.
Źródło:
Acta Physica Polonica A; 2015, 127, 5; 1552-1554
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fast Stochastic Reorientations in Nematic PAA and PAP
Autorzy:
Podsiadły, R.
Mayer, J.
Janik, J. A.
Krawczyk, J.
Stanek, T.
Powiązania:
https://bibliotekanauki.pl/articles/1963251.pdf
Data publikacji:
1997-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
35.20.Yh
24.50.Fq
61.30.Eb
Opis:
Incoherent quasielastic neutron scattering spectra were measured for nematic para-azoxyanisole (PAA) and para-azoxyphenetole (PAP) with the energy resolution of ca. 30 μ eV, at Dubna IBR-2 reactor. Data processing contained a careful background subtraction and the multiple scattering correction. The corrected spectra were subjected to a reorientational model fitting procedure. For PAA, a model of two convoluted reorientations - that of benzene rings coupled with the terminals and that of the whole molecule around the long molecular axis - gave a fairly good description of the quasielastic neutron scattering spectrum. For PAP, introducing a third motion - interconformational jumps in the ethoxy terminals - in addition to motions suggested for PAA, gave a good agreement with the measured quasielastic neutron scattering spectrum.
Źródło:
Acta Physica Polonica A; 1997, 91, 3; 513-518
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elastic Enhancement Factor: Mesoscopic Systems versus Macroscopic 2D Electromagnetic Analogue Devices
Autorzy:
Sokolov, V.
Zhirov, O.
Powiązania:
https://bibliotekanauki.pl/articles/1400563.pdf
Data publikacji:
2015-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.45.Gg
24.60.Lz
05.45.Mt
Opis:
Excess of probabilities of the elastic processes over the inelastic ones is a common feature of the resonance phenomena described in the framework of the random matrix theory. This effect is quantitatively characterized by the elastic enhancement factor $F^{(β)}$ that is the typical ratio of elastic and inelastic cross-sections. Being measured experimentally, this quantity can supply us with information on specific features of the dynamics of the intermediate complicated open system. We discuss properties of the enhancement factor in a wide scope from mesoscopic systems to macroscopic analogue electromagnetic resonators and demonstrate essential qualitative distinction between the elastic enhancement factor's peculiarities in these two cases. Complete analytical solution is found for the case of systems without time-reversal symmetry and only a few open equivalent scattering channels.
Źródło:
Acta Physica Polonica A; 2015, 128, 6; 990-993
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tensor Effects in Dipole Excitations at Finite Temperature
Autorzy:
Yüksel, E.
Bozkurt, K.
Powiązania:
https://bibliotekanauki.pl/articles/1399826.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
21.60.-n
21.60.Jz
24.30.Cz
Opis:
Tensor effects in the dipole excitation of neutron-rich $\text{}^{68}Ni$ nucleus are investigated in the framework of Skyrme-Hartree-Fock plus random phase approximation at finite temperature. We calculate isovector giant and pygmy dipole strengths with finite temperature random phase approximation by using different tensor correlations. The effect of both tensor and finite temperature on the giant dipole resonance-pygmy dipole resonance energy region is analysed. Pygmy dipole resonance calculations with different proton-neutron tensor coupling constants are also compared with the experimental results.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 320-322
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 22

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